In general, a packet based data transmission system, for example, a portable Internet system (WiMAX/WiBro: World Interoperability for Microwave Access/Wireless Broadband) or a wideband wireless access (BWA: Broadband Wireless Access), transmits data by applying a data transmission method using a dynamic resource allocation method so as to efficiently use radio resources. That is, the packet based data transmission system dynamically allocates resources to mobile stations through packet scheduling per frame.
In this instance, a control message, called a MAP, is used so as to broadcast resource allocation information to the mobile station for each frame. The MAP includes user information, a physical allocation of a burst, and a modulation and coding scheme (MCS) of the burst, which are transmitted from the corresponding frame.
Also, the portable Internet system has defined the scheduling classes, such as the unsolicited grant service (UGS), extended real-time polling service (ertPS), real-time polling service (rtPS), non real-time polling service (nrtPS), and best effort service (BE), for the purpose of achieving efficient uplink scheduling. The UGS and the ertPS are suitable for a periodical data service of a relatively less amount or a fixed amount of data, and are widely used since they are advantageous for the utilization of radio resources when traffic in a data service has periodicity such as the Voice Over Internet Protocol (VoIP) and a source rate of the traffic in the data service is variable.
However, the packet based dynamic resource allocation method generates a large amount of MAP overhead so as to support the traffic having the characteristic of the VoIP. Accordingly, the broadband wireless access system considers the circuit mode.
The circuit mode periodically allocates the resource of a fixed region to a specific user in a dedicated manner, and when the resource is allocated to the user, the mobile station has a usage right on the resource until a de-allocation occurs. In this instance, the MCS is also fixed so as to reduce the MAP overhead.
However, when the radio channel state is greatly changed, the above-noted resource allocation method is weak in relation to wireless transmission errors or reduces radio resource utilization, and it is therefore required to change the MCS. However, when the radio resource is de-allocated or the resource is changed according to the change of MCS, a region in which the radio resource is not used discontinuously may be generated.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.